Bitcode: Change reader interface to take memory buffers.

As proposed on llvm-dev:
http://lists.llvm.org/pipermail/llvm-dev/2016-October/106595.html

This change also fixes an API oddity where BitstreamCursor::Read() would
return zero for the first read past the end of the bitstream, but would
report_fatal_error for subsequent reads. Now we always report_fatal_error
for all reads past the end. Updated clients to check for the end of the
bitstream before reading from it.

I also needed to add padding to the invalid bitcode tests in
test/Bitcode/. This is because the streaming interface was not checking that
the file size is a multiple of 4.

Differential Revision: https://reviews.llvm.org/D26219

llvm-svn: 285773

1 files changed, 2 insertions, 1 deletions

diff --git a/clang/lib/Serialization/ASTReader.cpp b/clang/lib/Serialization/ASTReader.cpp
index 57de217078f..650c46e9ff0 100644
--- a/clang/lib/Serialization/ASTReader.cpp
+++ b/clang/lib/Serialization/ASTReader.cpp
@@ -3802,7 +3802,8 @@ static ASTFileSignature readASTFileSignature(llvm::BitstreamReader &StreamFile);
 
 /// \brief Whether \p Stream starts with the AST/PCH file magic number 'CPCH'.
 static bool startsWithASTFileMagic(BitstreamCursor &Stream) {
-  return Stream.Read(8) == 'C' &&
+  return Stream.canSkipToPos(4) &&
+         Stream.Read(8) == 'C' &&
          Stream.Read(8) == 'P' &&
          Stream.Read(8) == 'C' &&
          Stream.Read(8) == 'H';